Identification of a hormogonium polysaccharide‐specific gene set conserved in filamentous cyanobacteria
Identification of a hormogonium polysaccharide‐specific gene set conserved in filamentous cyanobacteria
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DOI：
10.1111/mmi.14566
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发表时间：
2020-07
影响因子：
3.6
通讯作者：
Esthefani G Zuniga;Kelvin K A Boateng;Nhi U Bui;Shadi Kurnfuli;Sawsan M. Muthana;Douglas D. Risser
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文献类型：
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作者：
Esthefani G Zuniga;Kelvin K A Boateng;Nhi U Bui;Shadi Kurnfuli;Sawsan M. Muthana;Douglas D. Risser
蓝细菌包含一个由产氧光合作用能力定义的门。该门的成员也经常活动。在半固体表面上表现出滑动或抽搐运动的菌株由保守的 IV 型菌毛系统 (T4P) 提供动力。在丝状形成异囊的蓝细菌中，运动通常仅限于称为激素的特殊丝，并且需要相关激素多糖（HPS）的沉积。参与 HPS 组装和输出的基因很大程度上未定义，并且假设 HPS 通过非典型的 T4P 驱动机制离开外膜。在这里，鉴定了几个主要编码糖基转移酶的新 hps 位点。突变分析表明，这些基因中的大多数对于 HPS 的运动和产生都是必需的。值得注意的是，大多数突变菌株积累了野生型细胞水平的主要菌毛蛋白 PilA，但没有细胞外 PilA，这表明 T4P 马达失调，因此，HPS 组装和 T4P 活性之间存在调节相互作用。蓝藻中 Hps 直系同源物的共现分析确定了一组扩展的假定 Hps 蛋白，其中包含 Wzx/Wzy 型多糖合成和输出系统的大部分成分。这意味着 HPS 可能是通过更规范的途径而不是 T4P 介导的机制分泌的。
Cyanobacteria comprise a phylum defined by the capacity for oxygenic photosynthesis. Members of this phylum are frequently motile as well. Strains that display gliding or twitching motility across semisolid surfaces are powered by a conserved type IV pilus system (T4P). Among the filamentous, heterocyst‐forming cyanobacteria, motility is usually confined to specialized filaments known as hormogonia, and requires the deposition of an associated hormogonium polysaccharide (HPS). The genes involved in assembly and export of HPS are largely undefined, and it has been hypothesized that HPS exits the outer membrane via an atypical T4P‐driven mechanism. Here, several novel hps loci, primarily encoding glycosyl transferases, are identified. Mutational analysis demonstrates that the majority of these genes are essential for both motility and production of HPS. Notably, most mutant strains accumulate wild‐type cellular levels of the major pilin PilA, but not extracellular PilA, indicating dysregulation of the T4P motors, and, therefore, a regulatory interaction between HPS assembly and T4P activity. A co‐occurrence analysis of Hps orthologs among cyanobacteria identified an extended set of putative Hps proteins comprising most components of a Wzx/Wzy‐type polysaccharide synthesis and export system. This implies that HPS may be secreted through a more canonical pathway, rather than a T4P‐mediated mechanism.